Volume 532, August 2011
|Number of page(s)||5|
|Section||Stellar structure and evolution|
|Published online||04 August 2011|
The masses of the neutron and donor star in the high-mass X-ray binary IGR J18027-2016⋆
Department of Physics & AstronomyThe Open University, Milton Keynes MK7 6AA, UK
2 Departamento de Física, Ingeniería de Sistemas y Teoría de la Señal, Universidad de Alicante, Apdo. 99, 03080 Alicante, Spain
3 School of Physics & Astronomy, Cardiff University, The Parade, Cardiff, CF24 3AA, UK
4 Division of Earth, Space & Environment, University of Glamorgan, Pontypridd, CF37 1DL, UK
Received: 2 June 2011
Accepted: 2 July 2011
Aims. We report near-infrared observations of the supergiant donor to the eclipsing high mass X-ray binary pulsar IGR J18027-2016. We aim to determine its spectral type and measure its radial velocity curve and hence determine the stellar masses of the components.
Methods. ESO/VLT observations of the donor utilising the NIR spectrograph ISAAC were obtained in the H and K bands. The multi-epoch H band spectra were cross-correlated with RV templates in order to determine a radial solution for the system.
Results. The spectral type of the donor was confirmed as B0-1 I. The radial velocity curve constructed has a semi-amplitude of 23.8 ± 3.1 km s-1. Combined with other measured system parameters, a dynamically determined neutron star mass of 1.4 ± 0.2–1.6 ± 0.3 M⊙ is found. The mass range of the B0-B1 I donor was 18.6 ± 0.8–21.8 ± 2.4 M⊙. These lower and upper limits were obtained under the assumption that the system is viewed edge-on (i = 90° with β = 0.89) for the lower limit and the donor fills its Roche lobe (β = 1 with i = 73.1°) for the upper limit respectively.
Key words: X-rays: binaries / binaries: eclipsing / stars: neutron / binaries: general / stars: individual: IGR J18027-2016 / stars: massive
© ESO, 2011
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